A surprising new study found daily caffeine consumption alters the brain’s structure. Specifically, those who regularly used caffeine had less gray matter volume in their brains compared to those that didn’t use the drug at all. The researchers caution that this doesn’t mean that caffeine causes negative cognitive effects. So, don’t throw out your coffee from the cupboard just yet.

It seems like every day there’s a new scientific study on coffee’s effects on our health. Some report that caffeine has positive effects while others report on its downsides. It’s not rare to find two different studies reaching two seemingly opposite conclusions. If you’re confused, you’re not alone.

Luckily, despite some occasional confusing conclusions, the net effect of caffeine seems to be positive. Moderate caffeine intake increases the metabolism promoting weight loss, reduces the risk of type 2 diabetes significantly, lowers the risk for cardiovascular diseases, and represents an important source of antioxidants.

Caffeine also seems to offer protective effects for the brain. Besides stimulating dopamine and glutamate, which makes you start feeling alert and awake, caffeine has been associated with slowing cognitive decline due to Alzheimer’s and Parkinson’s.

But that’s not all it does. While caffeine makes us more alert during the day, it can also disrupt sleep if consumed in the evening or close to bedtime. Previous research showed that sleep deprivation is associated with changes in the gray matter of the brain.

Gray matter, named for its pinkish-gray color, is home to neuronal cell bodies, axon terminals, and dendrites, as well as all nerve synapses. White matter areas of the brain mainly consist of myelinated axons, which form connections between brain cells.

In a new study, researchers from the University of Basel wanted to investigate more closely whether caffeine consumption can affect brain structure.

The researchers recruited 20 healthy individuals, all of whom drink coffee on a daily basis. Each participant was given tablets over two 10-day periods, during which they had to abstain from consuming any caffeine products.

During one 10-day window, the tablets that they were given contained caffeine, while in the other period the tablets had no active ingredient, acting as the placebo or control group.

At the end of each 10-day period, the subjects’ gray matter volume was measured by scanning the brain. Sleep quality was also assessed by recording the electrical activity of the brain with EEG.

The results were rather surprising. The data comparison between the two groups showed no significant differences in the depth and quality of sleep. In other words, those who ingested the caffeine tablets didn’t show signs of sleep deprivation.

However, the group that ingested the caffeine tablets saw a significant decrease in gray matter volume. The difference was particularly striking in the right medial temporal lobe, including the hippocampus, a region of the brain that is essential to memory consolidation, the researchers wrote. They add that these results are not actually concerning.

“Our results do not necessarily mean that caffeine consumption has a negative impact on the brain,” Dr. Carolin Reichert of the University of Basel said in a statement . “But daily caffeine consumption evidently affects our cognitive hardware, which in itself should give rise to further studies.” 

Previous studies that have analyzed gray matter in association with caffeine intake have tended to focus on older patients, rather than young healthy subjects as in the present study. This may explain why the kind of temporary neural plasticity reported by the study has not been observed before.

“The changes in brain morphology seem to be temporary, but systematic comparisons between coffee drinkers and those who usually consume little or no caffeine have so far been lacking,” says Reichert.

The findings appeared in the journal Cerebral Cortex.